Why Is Friday The 13th Unlucky?

Can you honestly say that you’ve never felt a slight pang of concern when waking up on the morning of Friday the 13th?

You’re not alone. Maybe it’s triskaidekaphobia, the fear of the number 13, that gets you down. But, if 13s don’t bother you unless it’s Friday, you might be susceptible to what’s sometimes known as paraskevidekatriaphobia or friggatriskaidekaphobia, instead. Whether you plan on purposely walking under ladders with black cats this Friday or staying tucked in bed, it’s worth diving into why Friday the 13th has a bit of a reputation.

Why do people fear the number 13?

First, let’s get into 13. While many cultures have an issue with the odd number, there’s no one set of circumstances that would make it decidedly unlucky. Common theories behind the fear of 13 include

Viking lore, where the unsavory Loki is believed to be the 13th god in the Norse pantheon

a biblical reference to the 13 people reportedly sitting at the table for Jesus’s last supper

numerology, where 13 is in low regard because it follows 12, a very “complete” number. But, if you ask an architect why they omitted the 13th floor from a high-rise, they probably won’t bother citing a source for their superstition.

Why is Friday the 13th unlucky?

Friday was named for one of two Norse goddesses, Freya or Frigga. While exclaiming “TGIF” is common now, some traditions consider “Frigga’s Day” to be unlucky. That’s not the only theory as to why Friday the 13th is unlucky though. Some Christians believe that Christ was crucified on a Friday. Friday was also once known as “hangman’s day” in ancient Rome and Britain because it was usually the day that condemned people would be hanged.

It’s likely that these two sets of unlucky lists just add up to make Friday and thirteen an intense combination for superstition. And of course, if you’re expecting unlukcy things to happen, you might even change your habits on days like this. Multiple studies speculate that businesses lose millions of dollars in revenue each Friday the 13th because some people avoid regular behaviors like traveling or making investments.